The present invention relates to the mechanical interlocking of electric apparatuses and devices, and more specifically the invention relates to an interlocking means that is effective for preventing the unintentional, simultaneous activation of two electrically connected apparatuses.
To be even more specific, the invention relates to an interlocking device arranged to be mechanically connected, directly or indirectly, to each one of two electric devices by means of a pair of plungers, received for sliding motion in the interlocking device. The plungers are received for reciprocating motion in parallel, and each plunger is formed to engage the associated electric apparatus such that the plungers are moved in a first direction upon closing the circuit, and in a second direction upon breaking the electric circuit. A blocking element, a portion thereof having a substantially quarter circular section, reaches transversally across the plunger paths. Said blocking element is rotatable about an axis, running in a dividing plane that is extended between the movement paths of the plungers. As one of the plungers is moved in the first direction, the blocking element is urged to pivot about the axis so as to block, with one side of the quarter circular portion, the motion path of the other plunger. Concurrently, the other side of said quarter circular portion engages the moved plunger which prevents the blocking element to rotate in the reversed direction as long as said plunger remains in the set position.
Switching apparatuses, such as relays and other connectors for power distribution to current consumers, are arranged in electric power supply centrals and switch gear apparatuses. In many such applications, there is a need for preventing the simultaneous closing of power circuits of two electrically connected and cooperating apparatuses, and securing that one apparatus always remains inoperable. A typical application is e.g. the starting operation of electric motors wherein, for load restricting reasons a lower startup current is fed to the motor by a first relay, while the full operative current successively is fed to the motor via a second relay when the motor has reached a preset rotational speed (so called YD-start).
Thus, the invention also relates to the specific implementation of the interlocking device in an assembly for distribution of starting power and operation power to an electric motor.
Electrically connected and cooperating apparatuses such as contactors often have different dimensions, and may thus have different length of travel in their closing and breaking motions, respectively. For a man skilled in this technical field, these differences present a problem when connecting apparatuses for cooperation. One such problem is the need for storage of differently sized connecting devices, the other and more substantial problem is reduced safety and operational stability.
The object of the invention is to provide a mechanical interlocking device by which these problems may be avoided.
The above object is met by the suggested interlocking device, that is structured to secure an interlocking function also between differently sized connected apparatuses having different lengths of closing motion.
Briefly, the invention suggests that each one of a pair of electrically connected or mechanically cooperating apparatuses engages a pair of plungers, received for sliding motion in a house. The plungers are received for reciprocating motion in parallel, and each plunger is formed to engage the electric apparatuses such that the plungers are moved in a first direction upon closing the circuit, and in a second direction upon breaking the electric circuit. A blocking element is engaged by the plungers such that the first plunger that is moved in said first direction blocks the path of movement for the second plunger as long as said first plunger remains in the set position.